The present invention relates to a fermentation process for production of citric acid from olefins. It has been well known that citric acid is produced by the assimilation of normal paraffins of C.sub.12-18 as carbon source to culture microorganisms.
Furthermore, it has been attempted to use paraffin wax as carbon source for the fermentation of hydrocarbons. But paraffin wax is in a solid state at fermentation temperature usually 25.degree. to 35.degree. C. It is necessary for the fermentation process to disperse the carbon source in the form of microparticles or to dissolve it in the culture medium. Then, many surface active agents were applied to improve the dispersion property of solid wax by many investigators for number of years. But the application of surface active agents is not completely adopted, because their dispersibility only displays in the concentration of about 3 percent weight of surface active agents to the culture medium; surface active agents hinder frequently the productivity of citric acid in cultivation; and the dispersibility of surface active agents is reduced by their rapid assimilation.
Taking it into consideration, the melting point of olefin is lower than the same carbon number of normal paraffin, the dispersion of olefins, especially having the carbon number more than 8, is superior to that of normal paraffins. On the background mentioned above, we, inventors, have made efforts to develop the fermentation process for the production of citric acid by assimilation of olefins.
Olefins less than the carbon number of C.sub.13 are in great demand as the raw materials for plasticizers and for synthetic detergents. However, olefins more than 14 are not in demand in the market and the present invention provides one of the profitable way of promoting the effective utilization of such olefins.
One of characteristic features of the present invention lies in the use of mixture of crude olefins as carbon source in the culture medium. As the mixture of crude olefins produced from thermal cracking of crude paraffin wax may be used as carbon source, the cost of the carbon source becomes cheaper. Therefore, the application of crude olefins for the process of the present invention is useful for the reduction of citric acid manufacturing cost.